1. Field of the Invention
Apparatus for emplacing a fastening element into a placement base, and use of the apparatus.
The invention relates to an apparatus for emplacing a fastening element into a placement base having a working piston for acting on the fastening element (4) upon emplacement, which piston includes a piston plate (11, 34) and a piston shaft (34) of a rigid, non-deformable material, the piston plate (11, 51) being displaceable in a piston guide sleeve (7) during a working stroke (31) out of a rest position into an end position and having in the working direction a ring-shaped stop surface (37) with respect to which there is arranged coaxially and at a spacing a ring-shaped counter-surface (43) of a receiving sleeve (38, 50) of a rigid, non-deformable material. The invention also pertains to a use of this apparatus for fastening components to the placement base with the aid of fastening elements.
2. Discussion of the Prior Art
There are known numerous apparatuses of this kind, which are employed for fastening the most varied components on placement bases of different kinds by means of fastening elements such as bolts, rivets, nails. Depending on configuration, the apparatuses work in single-shot operation, semi-automatically or fully automatically. Basically, all apparatuses are similarly constructed. A working piston is accelerated, mechanically or under the pressure of a medium, for example under pyrotechnically generated gas pressure. This working piston then drives for its part the actual fastening element. The apparatuses further have auxiliary devices which fulfil particular auxiliary functions or serve the reliability of their functioning or their handling. An example for such an auxiliary function is the return of the working piston after an emplacement procedure. Further auxiliary devices serve for example for the supply of the fastening elements and damping or buffering. Still further components such as for example housing parts fulfil functionally secondary purposes.
There is described in U.S. Pat. No. 4,441,644 an impact buffer for hammer apparatuses for hammering nails of the like, in which an impact piston, acted upon by compressed air, is guided in a cylinder and hammers the nail, located in the guide channel, into a placement base. The main inventive feature of this patent consists of the buffer system, of two buffer elements having differing geometries and materials, which in the case of blind shots, i.e. when inadvertently no nail is loaded, or in the case of energy excess due to an emplacement procedure in a placement basis of little resistance, is capable of absorbing this excess energy such that the apparatus or its functional parts remain undamaged and reliable even after multiple operations.
The functional process of the apparatus is as follows:
Upon actuation of a trigger arranged on the handgrip, compressed air flows into the cylinder chamber between the upper side of the impact piston and the guide cylinder. At a certain pressure the clamping connection between the head of the impact piston and a latching bush is released and the impact piston is moved by the compressed air out of its stand-by position into a braking position, whereby the nail is hammered into the placement base by means of the impact stroke. Upon impact of the impact piston on the first elastomeric buffer this is squashed, deformed and compressed. By these means there arises a certain spring path of a few mm, whereby excess energy is already exhausted to a great degree. In the case that further excess energy is present, the ring-shaped surface of the impact piston runs against a second elastomeric buffer which is located at the end of the guide cylinder. By means of this form fitting the impact piston is completely braked, there being attained an additional spring path of a few mm depending on the hardness and deformation of the second buffer element. After the impact procedure the impact piston is moved back into its stand-by position (rest position) again, by means of compressed air. A new nail can be loaded and the next impact procedure initiated. Disadvantageous with such an apparatus is the great spring path arising in the braking procedure, my means of which the apparatus is protected, but the placement accuracy is strongly affected. Differing braking procedures by the soft buffer system, due to differing nail lengths or fastening materials or placement bases lead to different depths of the nail heads in the fastening material (nail head flush or projecting or sunken).
A further compressed air driven impact apparatus is described in EP-A-661 140. The aim of this invention is to avoid a post-impacting of the impact piston or apparatus head, and wide area damage to the decorative fastening element caused thereby, due to the air compressed in front of the impact piston and the elastic receiving buffer. With this apparatus also the impact piston is softly braked via the receiving buffer form-fitting through elastic deformation with a certain spring path, and then is moved back into the initial position via air stored in a separate chamber.
Compressed air apparatuses of the kind described are employed primarily for driving nails into soft placement bases such as wood, i.e. the impact energy is relatively small. A further disadvantage is the connection of this kind of apparatus to stationary compressed air equipment via hose connections.
With harder placement bases such as concrete or steel, there are primarily employed bolt emplacement apparatuses having chemical/pyrotechnical drive by means of drive load cartridges, which thus allow free ranging fastening of bolts or nails.
The apparatus described in EP-A-732 178 can be considered as exemplary of such apparatuses. With this apparatus diverse configuration possibilities of modern apparatus developments are demonstrated, the technical features shown in the patent application being founded substantially on damping elements, braking elements and return springs of elastomeric materials.
The receiving procedure of the drive piston is effected relatively softly via the combined buffer and braking system due to the elastomeric properties of the component elements, the axial movement of the drive piston upon emplacement of a bolt or upon a blank shot being locally limited by means of the radial expansion of the braking element. The elastomeric compression spring provided for the piston return is thereby loaded to a high degree due to the dynamics of the emplacement procedure, whereby at least partial elements of the overall spring are taken to the blocking limit. Further, the spring path of the proposed return device is relatively small due to the specific properties of the selected construction having a plate structure and the material-specific properties of the elastomer, so that the structural length of the apparatus, in relation to a particular placement path (=bolt length) is considerable, Thereby, the bolt emplacement apparatus is relatively heavy and clumsy.
A further disadvantage consists in that the braking procedure of the drive piston in combination with the return spring and the braking buffer is undefined, since both the drive power, e.g. with different cartridges, and also the emplacement power, with different bolt lengths and different emplacement resistances (differing placement bases), strongly influence the overall braking and receiving procedure and thereby influence the quality of emplacement. Also, the elastomeric springs use a high percentage of the drive energy if they are strongly compressed for reason of a shorter structural length of the apparatus. This leads to a reduction of the emplacement performance of the apparatus.
A further possibility for piston return is shown in U.S. Pat. No. 3, 331,546. There, a plate-like arrangement of elastomeric plate springs is pressed together and compressed upon the advance of the drive piston, The full energy of the drive piston in the case of a blank shot, or the excess energy upon emplacement of bolts in a light placement base, must be taken up by the overall spring material. With regard top structural length, exactitude of emplacement depth and energy consumption, what is said above applies also to this apparatus.
DE-A-2 632 413 shows a bolt emplacement apparatus having and elastic damping packet which consists of a series of ring pairs arranged one behind another, Here, the application of the braking force of the drive piston is effected via a moveable braking ring, which upon advance of the drive piston is pressed against the damping packet by the gas pocket building up between piston head and receiving ring. The advantage of this arrangement lies in that, due to the relative movement of the receiving ring, the impact forces of the drive piston are reduced in the braking procedure. Drive piston, receiving ring and damping packet are thereby form-fittingly connected.
A further braking and receiving system for a pyrotechnically driven drive piston is described in U.S. Pat. No. 4, 824,003. There, the buffer system consists of a conical braking ring into which the drive piston head runs formfittingly with its likewise conical part. Arranged after this braking ring is a ring-shaped arrangement of two parts which are elastically and plastically deformable. Thereby, the drive piston can be received in a defined manner and the excess emplacement energy absorbed by the braking system. An automatic piston return is not provided with this apparatus. Conical receiving and braking systems achieve, with the relatively high running velocities of the drive piston, very high surface compressions, since due to the manufacturing tolerances of the two conical surfaces, naturally, the entire conical surface never corresponds in a form-fitting manner, rather only a small partial region. There thus arise local overloads upon form- fitting together, which lead to material damage of the drive piston or braking ring due to plastic deformation.
The object of the present invention is seen in the,
provision of an apparatus of the kind mentioned in the introduction, which is so conceived that it not only optimally fulfils the basic functions but also various auxiliary functions, and is so conceived that numerous variants in the configuration and use of the apparatus are possible; and
proposal of a use of the this apparatus.